To ALL: at this moment the Rainbow Sentinel Dragon is for sale (in Europe for 14,99 euro's). This is the BEST overall fighter you'll ever gonna get.
Mine is lvl 15, and he wins 90% of each tournament for me.
If you EVER wanna buy something on DS, now is the time! (and no, I don't have shares in S8 or TL).
To beat:
Colors, use Rainbow Sentinel
Diamonds, use Diamonds
Diamond-hybrids, use Diamond-hybrids with a different base-color
Pink-purple-hybrids, use Jade